1. Field of The Invention
The invention relates to detachable fastening means for use with the heat sink of a CPU set, and particularly to a customized fastening means for use therewith.
2. The Related Art
Traditional clips for fastening a heat sink to a CPU, is generally of one piece as shown in U.S. Pat. No. 5,602,719. Such clip includes a resilient strip type main body with two locking tags at two opposite ends for respectively latching to the socket under the CPU whereby the strip type main body will be deflected to exert a force for pressing against the heat sink and firmly attaching the heat sink to the CPU. Simultaneously, the clip may further include a handle at one end for easy operation of the clip with regard to the heat sink and the associated CPU set.
One disadvantage of the conventional clip is that such one-piece clip can not accommodate the variation in dimension of the size of the socket because the spring force changes considerably even with the small variation. Another disadvantage is that the clip should produce two, i.e., one biasing and one retention, forces from the same spring constant--one between the tags of the clip bearing on the sidewalls of the socket and the other bearing against the top surface of the heat sink through flexing of the top member. This inherent requirement results in high tolerance and precision of the clip itself and difficulties in manufacturing. In other words, the clip should effect engagement not only between the heat sink and the CPU but also between the clip and the socket. From another viewpoint, because the clip is of one piece providing both aforementioned engagements, it is difficult to achieve a fast, easy and delicate release of the clip from the socket while maintaining the required sufficient pressing force derived from the strap type main body of the clip and imposed on the heat sink.
Accordingly, U.S. Pat. Nos. 5,600,540 and 5,671,118 introduce a two-piece retainer clip for use with the heat sink wherein one piece is an elongated strap having a bent portion that bears down on the heat sink to force it into a heat conducting relationship with the CPU thereunder and also includes one locking tag with a first latching opening at one end of the strap for being hooked on one corresponding protrusion or lug on the side wall of the socket. The second piece is rotatably mounted on the end of the strap opposite to the locking tag and when forced down and rotated inward, a second latching opening will hook on the other corresponding protrusion or lug on the other side wall of the socket. Regardless of whether the aforementioned two-piece type clip fully overcome the shortcomings of the one-piece type clip, there is a concern regarding the strap which is still used, with its one end, to latch itself unto the socket and then still owns one aforementioned shortcoming of the one piece type clip. Additionally, because the second piece is substantially freely rotatably mounted to the first piece for easy and fast releasing the whole retainer clip from the socket, this swinging structure arrangement generally diminishes the originally designed biasing force to the heat sink. Thus, when a relative huge heat sink is applied to the CPU set, it is questionable whether this swinging type retainer clip can achieve the required relatively large biasing force against the heat sink for assuring the reliable and tight engagement between the heat sink and the CPU during a severe vibration situation.
Therefore, an object of the invention is to provide a retaining clamp device for use with the heat sink of CPU set, which generally avoids the aforementioned shortcomings of the existing retainer clip used for the CPU set.